The effect of pressure on luminescence properties of Cr3+ ions in LiSc(WO4)2 crystals-Part I: Pressure dependent emission lineshape

We report the results of high-pressure studies of spectral properties in Cr3+-doped LiSc(WO4)2 crystals between ambient pressure and 260 kbar. The effect of pressure on the present system has led to a structural transformation for pressure 60-88 kbar and a low-field → high-field spectral transformation of the Cr3+ emission for pressure 117-227 kbar. The pressure-induced spectral transformation provided the opportunity to distinguish two distinct Cr3+ sites in the host lattice. We have attributed them to the Cr3+ ions that occupy the Li+ and Sc3+ sites. For both sites we observed that energy of the 2E excited state of Cr3+ was lower than 14,000 cm−1 and exhibited pressure-induced red shift of about −2.5 cm−1/kbar. We have also observed the large inhomogeneous broadening of the 4T2→4A2 and 2E→4A2 emissions. We have completed a quantitative analysis of the relative emission intensities of the 2E→4A2 and 4T2→4A2 transitions as a function of pressure and temperature to study the distribution of the crystal field and electron-phonon coupling of the Cr3+ in the host lattice. As the result we have recovered a functions that describe the distribution of the energy of 4T2 state and electron-lattice coupling (S-12)ℏω in considered material.